1. Field of the Invention
The present invention relates to a long distance telephone call limiting device capable of preventing the user of an ordinary dial type telephone from making long distance telephone calls without permission of the owner.
2. Description of the Prior Art
The long distance telephone service in the United States and its surrounding area are conducted according to the following system:
The entire service area is divided into telephone areas to which a three digit area code is assigned. This area code is put before a 7 digit individual number, thus constituting an individual telephone number. Of course, within a local call area no area code is required. The manner of combination of the above mentioned area codes and that of the first three figures of 7 digit individual numbers are fundamentally different from one another. For example, the figure in the middle of three digits of each area code is 0 or 1 such as, for example, 205, 712 but the figure in the middle of the first three figures of each 7 digit personal number is never to be 0 or 1, such as, for example, 245, 837, etc.
Thus, it is concluded from the above mentioned telephone number composition that there are three areas for making long distance calls, namely:
1. An area where an area code plus an individual number are dialed.
2. An area where the dial numeral 1 (a long distance call number) and then an area code and an individual number are dialed.
3. An area where 0 is dialed for calling an operator and telling her the area code and individual number desired.
In summation, in order to make long distance calls in the above mentioned areas, one must dial 0 or 1 in the first order, or 0 or 1 in the second order without exception, and this is not applicable to local calls. Accordingly, if a means is provided on the telephone which prevents the first digit 0 or 1, or the second digit 0 or 1 from being dialed initially it is possible to prevent any long distance telephone calls.